1. Field of the Invention
The present invention concerns alpha-3 chain type IV bovine and human polynucleotides and peptides expressed by such polynucleotides which are useful in detecting Goodpasture antibodies and treating Goodpasture syndrome.
2. Background Information
The major structural component of mammalian basement membranes, type IV collagen, is composed of a number of distinct polypeptide chains (Timpl et al. 1981; Martin et at 1988; Timpl 1989). The most abundant species, .alpha.1(IV) and .alpha.2(IV) have been extensively characterized in man and mouse and an .alpha. type chain from Drosophila also been identified (Soinimen et al. 1987; Blumberg et al. 1988; Hostikka and Tryggvason 1988; Saus et al. 1989; Muthukumaran et al. 1989). Characteristics of these collagens include a highly conserved carboxy-terminal noncollagenous (NC1) domain of .about.229 residues, a shorter amino-terminal globular domain (7S domain) and a triple helical collagenous domain, in which interruptions occur in the Gly-Xaa-Xaa-Yaa repeat motif, giving a degree of flexibility to the triple helix. Within the membrane matrix the individual collagen chains exist as heterotrimer, which form a supra-molecular structure via interactions between the 7S domains of 4 molecules and the NCI domains of 2 heterotrimers (Timpl et at 1981).
Bacterial collagenase digestion releases the NCI domains from the other components of basement membrane as hexamers, comprised of the 3 NC1 domains from each of 2 interacting collagen heterotrimers. The NCI domains can be further separated on the basis of molecular weight by denaturing polyacrylamide gel electrophoresis. This results in a number of separate monomeric and dimeric subunits (Mr=24,500-28,300 and 40,000-50,7000 respectively), including several which are distinct from the .alpha.1(IV) and .alpha.2(IV) chains (Butkowski et al. 1985; Wieslander et al. 1985). The monomeric subunits that result from collagenase digestion of human glomerular basement membrane (GBM) have been termed M24, M26, M28+++ and M28+, while the equivalent subunits of bovine basement membranes have been termed Mla, Mlb, M2, and M3 (Kleppel et al. 1986; Butkowski et al. 1987). M24 (or M1a) and M26 (or M1b) are the NC1 domains of the .alpha.1(IV) and .alpha. 2(IV) chains. M28+++ (or M2*) and M28+ (or M3) are the NCI domains of 2 novel collagen chains termed .alpha.3(V) and .alpha.4(V). Short segments of the junction between the collagenous and NCI domains of human and bovine .alpha.3(IV) and .alpha.4(IV) peptides have been sequenced, confirming that they have a type IV collagen structure (Saus et at 1988; Butkowski et al. 1990).
The .alpha.3(IV) chain and the .alpha.4(IV) chain are of particular interest as such chains have been implicated in the pathogenesis of Goodpasture syndrome and Alport-type familial nephritis, clinical syndromes that affect GBM and cause functional kidney impairment (Hudson et al. 1989). Goodpasture syndrome is an autoimmune disorder characterized by glomerulonephritis, lung hemorrhage and anti-GBM antibody formation (Glassock et al. 1986). The nephritis and lung damage are mediated by these anti-GBM antibodies which are primarily targeted at the NCl domain (M28+++) of .alpha.3(IV) (Butkowski et al 1985; Wieslander et al. 1985; Kleppel al.1986). Alport syndrome is an inheritable disorder characterized by glomerulonephritis, sensorineural hearing loss and various abnormalities of the lens of the eye (Grunfeld, 1985). Ultrastructural GBM abnormalities frequently observed in the syndrome include thinning, diffuse splitting and multilamination of the lamina dense (Hinglais et al. 1972; Yoshikawa et al. 1981). Several investigators have reported that the GBM of some individuals with Alport syndrome does not react in vitro with Goodpasture antibodies nor with a monoclonal antibody that recognizes a Goodpasture epitope, suggesting that there is an abnormality of the .alpha.3(IV) chain in these patients (Olsen et at 1980; Jenis et al. 1981; Jeraj et al. 1983; Kashtan et al. 1986; Savage et at 1986; Kleppel et al. 1987).
Recently a gene encoding another novel human type IV collagen chain, COL4A5, was cloned, on the basis of homology with the .alpha.1(IV) and .alpha.2(IV) chains (Hostikka et al. 1990; Myers et al. 1990). The existence of such a chain had not been expected from biochemical or immunological studies of GBM (glomerular basement molecular), and yet antibodies raised to a peptide fragment synthesized from the predicted amino acid sequence of .alpha.5(IV) localized this chain to the GBM (Hostikka et at 1990). COL4A5 maps to Xq22, a region known from genetic linkage studies to contain a locus for Alport Syndrome (Atkin et al. 1988; Brunner et al. 1988; Flinter al. 1988). Further, COL4A5 has been shown to be mutated in 3 of 18 large kindreds with the disease (Barker et al. 1990).